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I forked a project that was dual licensed under the GPL and a commercial license. Since my code was open source and the GPL being what it is, I started by releasing my app under the GPL.

But now I'm thinking about dual licensing the project and can't figure out what to do. Since I have copyright on a majority of the code (most of the code was either rewritten or new), can I just pick a commercial license or do I have to buy the upstream commercial license since I'm technically a "derivative" of the project?

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2 Answers 2

up vote 4 down vote accepted

Since you have the copyright on the majority of the code. If you were to remove anything that you didn't write and then rewrite it yourself, then you would be the sole copyright holder and hence able to license it however you wanted.

Disclaimer: I'm not a lawyer, this isn't legal advice

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I would really like to do this but there are major parts of some core code that work just fine and shouldn't be rewritten. –  TheLQ Feb 27 '11 at 16:44

If you forked the project under the GPL, then any code you added to it is also GPL, and you cannot license it under any non-GPL friendly license.

But if you forked the project under the commercial license, then any changes that you've made would be subject to the definition of the commercial license.

What is the commercial license, and what constraints are bound on it's usage? Does the commercial license even allow you to make changes to the code or relicense the code? For the commercial license, you'll have to read the details.

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A subtle but important distinction, he may have forked the GPL'd code, but only the other copies released under the GPL of the the derivative code are affected by this. There is nothing stopping the author from commercially licensing the original code and then, provided the commercial license allows, commercially license his additions. –  Thomas James Nov 13 '11 at 21:09
    
TL;DR The GPL is a distribution license, it doesn't apply if the code/binaries aren't distributed. –  Thomas James Nov 13 '11 at 21:10

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